1. Field of the Invention
This invention relates to integrated circuit (IC) technology and more particularly. to an IC mounting board for use to mount an IC module and at least one bypass capacitor thereon.
2. Description of Related Art
An IC mounting board is a circuit board designed in particular to mount an IC module thereon. Customarily each power pin of the IC module is connected to a bypass capacitor for the purpose of filtering out any AC components in the power being supplied to the internal circuit of the IC module. The IC mounting board is typically designed with a complex layout of circuit lines used for connection with the pins of the IC module. Since an IC module typically includes a great number of pins, the layout of the circuit lines on the IC mounting board is highly complex to carry out.
A conventional IC mounting board is depicted in the following with reference to FIGS. 1 and 2; wherein FIG. 1A is a schematic top view of the conventional IC mounting board (designated by the reference numeral 100), and FIG. 1B is a schematic side view of the same.
As shown, the conventional IC mounting board 100 including an array of IC soldering points 110 for mounting an IC module 115 thereon through soldering means. Moreover, the IC mounting board 100 includes a plurality of paired SMD (Surface Mounted Device) soldering points 120 arranged around the area defined by the IC soldering points 110, each pair being used to mount a bypass capacitor 125 thereon through soldering means. In this preferred embodiment, for example, the IC module 115 is packaged through the Ball Grid Array (BGA) technology, while the bypass capacitor 125 is an SMD component. There exist, however, some drawbacks to this IC mounting board.
First, the chip (not shown) contained in the BGA-packaged IC module 115 is typically mounted on a small multi-layer printed circuit board (PCB) and electrically connected to the IC soldering points 110 via the printed wires and tin balls on the multi-layer PCB. In order to make the IC module more compact, the number of layers in the multi-layer PCB should be minimal, typically two. The power pins of the IC module 115 are typically arranged in the middle of the bottom side for the purpose of reducing the overall length of the power transmission lines between the IC module 115 and the power supply (not shown). Conventionally, however, the soldering points 120 are arranged outside the area defined by the IC soldering points 110 as illustrated in FIG. 1A, and moreover, these soldering points 120 are separated from the IC module 115 by a distance so that they would not impede the mounting and dismounting of the IC module 115 For these reasons, the bypass capacitor 125 are mounted considerably far away from the power pins of the IC module 115, and therefore, the elongated power transmission path between the bypass capacitor 125 and the power pins (not shown) of the IC module 115 would cause the bypass capacitor 125 to provide the bypass effect less effectively. Therefore, an increased number of bypass capacitors should be provided to enhanced the bypass effect. For instance, in the case of using four different power supplies in the IC module 115, it requires the use of a doubled number of bypass capacitors, i.e, eight, to provide satisfactory bypass effect to the power supply lines.
Moreover, in the case of the IC module 115 having a large number of pins, the conventional arrangement of the bypass capacitors 125 around the IC module 115 would cause the layout design for the IC mounting board to be very difficult to carry out. Typically, a chipset IC module for computer motherboard may have several hundreds of pins that require the same number of circuit lines on the IC mounting board for interconnection. Therefore, the arrangement of the bypass capacitor 125 around the IC module 115 would greatly complicate the layout design work for the IC mounting board. The circuit lines on the IC mounting board may need to be detoured to avoid the bypass capacitors 125. The lengthened signal transmission path may then affect the quality of the data signals being transmitted thereover. Solutions to this problem include the use of multi-layer PCB3 with more layers or a large PCB to implement the IC mounting board. These solutions, however, would undesirably increase the manufacturing cost.
Still moreover, the arrangement of the bypass capacitors 125 around the IC module 115 would impede the mounting and dismounting of the IC module 115. For instance, in the case of the IC module 115 being a BGA package, the mounting and dismounting of the IC module 115 requires the prior dismounting of the bypass capacitors 125, thus making the disassemble work very difficult and laborious to carry out.